fix(theme): cursor_shape = filledBox to match Linux terminal default

Per operator: "default cursor should mimic Linux's terminal cursor
size and behaviours!"

Linux terminals (gnome-terminal / xterm / konsole / Alacritty / kitty)
all default to a steady FILLED BLOCK cursor that fills the entire
cell. WT calls this `filledBox`. The previous default was `bar`
(thin vertical line) which is a Windows convention, not Linux.

mios.toml:
  cursor_shape = "filledBox"   (was "bar")

mios-config.html:
  cursor_shape dropdown now lists filledBox FIRST as "Linux default";
  added doubleUnderscore option for completeness.

Cursor BLINK behavior: WT inherits the blink rate from Windows
global keyboard settings (Control Panel -> Keyboard). There is no
per-profile blink-rate / blink-on/off setting in WT; the Linux
default behavior (~530ms steady-blink) maps to Windows' default
cursor blink rate, so the operator gets the expected feel without
any further config.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Kabuki94

usr/share/mios/configurator/index.html

@@ -499,13 +499,14 @@ <h1>MiOS configurator <span class="v" id="v-meta">schema 1.2.0 / mios 0.2.4</spa
           <option value="mica">mica</option>
           <option value="default">default</option>
         </select>
-        <label for="f-theme-cursor">cursor_shape</label>
+        <label for="f-theme-cursor">cursor_shape (filledBox = Linux default)</label>
         <select id="f-theme-cursor" data-key="theme.cursor_shape">
-          <option value="bar">bar</option>
-          <option value="filledBox">filledBox</option>
-          <option value="emptyBox">emptyBox</option>
+          <option value="filledBox">filledBox (block, Linux default)</option>
+          <option value="bar">bar (thin vertical line)</option>
+          <option value="emptyBox">emptyBox (block outline)</option>
           <option value="underscore">underscore</option>
           <option value="vintage">vintage</option>
+          <option value="doubleUnderscore">doubleUnderscore</option>
         </select>
         <label for="f-theme-scroll">scrollbar_state</label>
         <select id="f-theme-scroll" data-key="theme.scrollbar_state">

usr/share/mios/mios.toml

@@ -1318,7 +1318,7 @@ mode                = "dark"             # "dark" | "light" (rare; vendor=dark)
 acrylic             = true               # WT useAcrylic ON
 opacity             = 50                 # WT opacity 0..100 (50 = 50% transparency)
 system_backdrop     = "acrylic"          # WT 1.18+ per-profile backdrop
-cursor_shape        = "bar"              # WT cursorShape
+cursor_shape        = "filledBox"        # block-style cursor mimics Linux terminal default (gnome-terminal / xterm / konsole steady block)
 scrollbar_state     = "hidden"           # no scrollbar -- frame uses every col
 padding             = "0"                # zero padding -- frame flush to edges
 suppress_app_title  = true               # WT doesn't override our title